1. Field of the Invention
The present invention relates to display technology, and more particularly, to a blue phosphor for a fluorescent display and a method for synthesizing the same.
2. Description of the Related Art
Fluorescent displays, in particular, field emission displays (FEDs) are flat-panel displays driven by the same operating principle as cathode ray tubes (CRTs), and are constructed such that a cathode plate, which is a field emitter array (FEA) panel emitting electrons by an electric field rather than by thermions, and an anode plate, which is a fluorescent panel receiving electrons to emit light, are a predetermined gap spaced apart and packaged in high vacuum state.
Conventional CRTs generally employ sulfide-based phosphors which are good in color purity and luminous efficiency. However, if FEDs, in which a space between a cathode plate and an anode plate is short, use a high voltage of 10 kV or greater like in CRTs, discharge occurs. Thus, FEDs use a low voltage of 5 kV or less. In particular, in order to develop FEDs operable at a voltage as low as 1 kV or less, various researches are globally being carried out.
However, if the electronic energy is as low as 1 kV or less, electrons can only be scanned as deep as 20 nm from a phosphor surface. Thus, the efficiency, particularly luminescence, of a phosphor for a low-voltage operating FED is considerably lower than a CRT operating at a high voltage. Also, the surface state of a phosphor greatly affect the luminous efficiency thereof.
In particular, when a conventional sulfide blue phosphor, ZnS: Ag, Al, which has been widely used in CRTs, is used as an FED phosphor, it exhibits bad luminous efficiency and color purity at low voltages. Also, prolonged E-beam scanning gives rise to desorption of a trace of sulfur from sulfide-based phosphors, resulting in a decrease in the internal vacuum degree for smaller volume in the case where the distance between a cathode plate and an anode plate is approximately 1 mm like in an FED panel or impairing an FEA, thereby deteriorating display performance. To address such problems, vigorous research into oxide-based phosphors free from the risk of desorbing sulfur therefrom has recently been made.
For variety of applications, there is increasing demand for phosphors capable of exhibit high luminescence at low production cost. In order to reduce the production cost, not only the source material cost but also the processing cost required for manufacturing phosphors must be low. In current actuality, the major factor in the processing cost is the firing temperature in the course of synthesis. Under the circumstances, in order to obtain low-cost phosphors, it is quite important to synthesize highly luminescent phosphors that can be synthesized at a low firing temperature.